Corticofugal Regulation of Central Auditory Sensitivity

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Humans, and animals process auditory information carried by complex sounds so easily and so fast. This efficient signal processing is based on enormous computation taking place in the central auditory system. Auditory physiologists have explained that auditory signal processing or the response properties of central auditory neurons are resulted from divergent and convergent projections within the ascending auditory system. However, recent studies have shown that the corticofugal (descending) system plays a very important role in signal processing. It has been suggested that the corticofugal system regulates subcortical auditory signal processing through a highly focused positive feedback which works together with a wide spread lateral inhibition. Using bats as a mammalian model system, this proposal will collect data from three hypothesis-driven experiments in order to form a hypothetical working model for corticofugal regulation of midbrain auditory information processing. These studies involve electrophysiology and iontophoresis under free field stimulation conditions. Specifically, this application will study (1) how corticofugal system may facilitate or inhibit auditory response properties of neurons in the external and central parts of a midbrain auditory nucleus (the inferior colliculus) (2) how neurons in these two parts of the inferior colliculus may interact during sound stimulation and (3) the possible neurotransmitters that may be involved in these auditory information transmissions. The proposed study of the corticofugal system will contribute significantly to the development of a more realistic and dynamic model of central auditory signal processing. In particular, the data to be collected will help understand how the corticofugal system contributes to the optimization and reorganization of ascending auditory signal processing in subcortical auditory nucleus. This proposed study will advance our understanding of the functional role of the corticofugal system during central acoustic signal processing which has been given little attention until recently.